1. Field of the Invention
The present invention is directed to a process for the preparation of optionally cellular polyurea elastomer moldings which have improved surface quality and to the polyurea elastomers prepared by this process.
2. Description of the Prior Art
Reaction injection molding processes for the production of optionally cellular polyurea elastomers have been described in U.S. Pat. Nos. 4,433,067, 4,444,910 and 4,530,941. U.S. Pat. No. 4,774,263 is directed to the production of polyurea elastomers using a mold release agent. This reference discloses that suitable mold release agents are the salts of fatty acids having at least 12 carbon atoms and either primary mono-, di- or polyamines containing 2 or more carbon atoms or amines containing amide or ester groups and having at least one primary, secondary or tertiary amino group according to U.S. Pat. No. 3,726,952; blends of two or more of the following in accordance with British Pat. No. 1,365,215: (1) esters of monofunctional and/or polyfunctional carboxylic acids which contain -COOH and/or -0H groups and have OH or acid numbers of at least 5, (2) natural or synthetic oils, fats or waxes and (3) salts according to U.S. Pat. No. 3,726,952; salts of saturated or unsaturated aliphatic or cycloaliphatic carboxylic acids having at least 8 carbon atoms and tertiary amines which do not contain amide or ester groups in accordance with U.S. Pat. No. 4,098,731; and reaction products of ricinoleic acid and long chain fatty acids in accordance with U.S. Pat. No. 4,058,492. In addition, U.S. Pat. Nos. 4,396,729 and 4,764,540 disclose polysiloxane-based internal mold release agents for use in the production of polyurea elastomers.
Finally, U.S. Pat. Nos. 4,519,965 and 4,581,386 are directed to the use of internal mold release agent mixtures for either polyurethane and/or polyurea elastomers which are based on a zinc carboxylate and a solubilizer to maintain the zinc carboxylate in solution in the isocyanate-reactive component used to prepare the elastomer. One of the problems associated with the use of zinc carboxylates as mold release agents for the production of polyurea elastomers is that the surfaces of the resulting elastomers are unacceptably porous and rough.
An object of the present invention is to overcome these difficulties and improve the surface quality of polyurea elastomers prepared using zinc carboxylates as the mold release agent. This object can be achieved in accordance with the present invention as described hereinafter.